The present invention relates to devices for injecting, delivering, administering, infusing or dispensing a substance or product, and to methods of making and using such devices. The product or substance may be a medicament or therapeutic substance, for example, a growth hormone, insulin, etc. In some preferred embodiments, an injection device in accordance with the present invention comprises an automatic dispensing system and an energy source, for example, a drive spring, which supplies energy for a dispensing operation. In some preferred embodiments, the present invention relates to a brake mechanism for decelerating a moving part of an injection device for administering a product or substance.
In injection devices known from the prior art in which an output element acting on a product container is driven by a spring, allowance is specifically made for inserting a product container when determining how the device operates. Since the product has to flow through a narrow passage during the dispensing operation, such as a needle, a damping effect is generated due to the viscosity of the product which opposes the force of the output element so that the output element remains at a relatively low speed level. The relatively low speed level results in relatively low impulses or impacts when one moving part or component hits another part or component in the injection device, which has a positive effect on the service life of the device. However, this is only true if a product container has been inserted in the device. If a user initiates a product dispensing operation without inserting a product container, for example, there is no damping effect. This can lead to extreme acceleration values in the mechanism of the injection device, causing very high impulses or impacts when parts make contact with one another, which has a negative effect on the service life of the device. As a result, the device may be so severely damaged that it can no longer be used to administer injections. Increasing the dimensions accordingly, e.g. to absorb or counter impacts on or between moving parts, would increase the size of the device, making it seem clumsy.
Furthermore, a situation can arise in which, when a new ampoule is inserted, the output element does not contact with the plunger. This will be the case if, for example, the output element is pushed too far back during the process of changing the ampoule or if an ampoule which is only partially full is inserted. In this situation, too, extreme acceleration values can occur during the idle stroke of the output element, e.g. the portion of the stroke effected by the output element until it makes contact with the plunger of the ampoule. If a needle is not fitted on the ampoule in such a situation, the product in the ampoule is compressed due to the impact of the output element, causing an increase in pressure, potentially causing the product to be dispensed in an uncontrolled manner when a needle is fitted on the injection device.